NOTE: Important charges and non-bonding electrons are shown throughout the animation except during the transition state phase.
Click the structures and reaction black arrows in sequence to view the 3D models and animations respectively
The unstabilised phosphonium ylids are formed from the reaction of a phosphine usually triphenylphosphine with an alkyl halide e.g. ethyl bromide to give a phosphonium salt. This is then deprotonated using a strong base (NaH in this example but usually BuLi) to give the unstabilised ylid which can undergo a Z-selective Wittig reaction.